There are large amounts of data which are written once to a data storage device and then subsequently only read rarely and examples include archival storage of email and secondary geo-distributed replicas of data. On the rare occasions that this data is read, timely access is required and so use of magnetic tape based solutions (where robotic arms fetch tapes from a library and insert them into tape drive where they are mechanically wound to the correct point), which are typically used for cold storage, is not appropriate because of the high access latency. Tapes can also be affected by environmental conditions (e.g. humidity) and so durability may be limited. Existing storage solutions which provide low latency access are based on physical hard disks and solid state drives; however these have a high power consumption and are also expensive to buy.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known storage solutions.